This research program addresses human responses to the thermal environment in health and disease. The thermal environment will be characterized by physiologists and engineers in terms of the effects of clothing, buildings and environmental control systems with special emphasis on the heat and water vapor transfer through clothing. Man adapts to long-term thermally stressful conditions through acclimation and acclimatization, and the mechanisms of these adaptations will be studied as they relate to fitness and physical activity. The ability to defend against thermal stress shows considerable variation with age, state of physical fitness and previous exposure. The ability to predict the adequacy of such physiological defenses will allow the identification of specially vulnerable groups in the population. Such groups account for the substantial increases in daily mortality in heat waves and cold waves. An important mechanism in thermoregulation is that of behavioral responses. These responses are driven by thermal sensation and sensations of thermal comfort and discomfort. Since these behavioral drives are closely associated with the physiological responses, they will be studied in the same experiments and in the same subjects. Reductions in ventilation rates are a likely strategy in pursuing energy conservation. Such reductions will tend to decrease indoor air quality in terms of odors, tobacco smoke and irritants. We will pursue basic studies of the relationship between ventilation rates and indoor quality. Thermal and non-thermal effects of microwave radiation will be studied in another sub-project using specially trained and instrumented squirrel monkeys and well defined microwave fields.